Lipid Bilayers Are Long-Lived on Solvent Cleaned Plasma-Oxidized poly(dimethyl)siloxane (ox-PDMS).

K M Rifat Faysal,Anand Bala Subramaniam,Luis Garcia,June S Park,Jonny Nguyen

doi:10.1371/journal.pone.0169487

K M Rifat Faysal, Anand Bala Subramaniam + Show 3 more

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https://doi.org/10.1371/journal.pone.0169487

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Journal: PloS one	Publication Date: Jan 4, 2017
Citations: 11	License type: CC BY 4.0

Affiliation: University of California, Merced

Abstract

Although it is well known that phospholipids self-assemble on hydrophilic plasma-oxidized PMDS surfaces (ox-PDMS) to form cell membrane mimetic bilayers, the temporal stability of phospholipid membranes on these surfaces is unknown. Here we report that phospholipid bilayers remain stable on solvent-cleaned ox-PDMS for at least 132 hours after preparation. Absent solvent cleaning, the bilayers were stable for only 36 hours. We characterized the phospholipid bilayers, i) through quantitative comparative analysis of the fluorescence intensity of phospholipid bilayers on ox-PDMS and phospholipid monolayers on native PDMS and, ii) through measurements of the diffusive mobility of the lipids through fluorescence recovery after photobleaching (FRAP). The fluorescence intensity of the phospholipid layer remained consistent with that of a bilayer for 132 hours. The evolution of the diffusive mobility of the phospholipids in the bilayer on ox-PDMS over time was similar to lipids in control bilayers prepared on glass surfaces. Solvent cleaning was essential for the long-term stability of the bilayers on ox-PDMS. Without cleaning in acetone and isopropanol, phospholipid bilayers prepared on ox-PDMS surfaces peeled off in large patches within 36 hours. Importantly, we find that phospholipid bilayers supported on solvent-cleaned ox-PDMS were indistinguishable from phospholipid bilayers supported on glass for at least 36 hours after preparation. Our results provide a link between the two common surfaces used to prepare in vitro biomimetic phospholipid membranes—i) glass surfaces used predominantly in fundamental biophysical experiments, for which there is abundant physicochemical information, with ii) ox-PDMS, the dominant material used in practical, applications-oriented systems to build micro-devices, topographically-patterned surfaces, and biosensors where there is a dearth of information.

Highlights

Nanometric phospholipid bilayers supported on a solid surface are cell membrane mimetic in vitro constructs useful for fabricating biosensors[1,2,3,4,5,6] for studying membrane biophysics[7,8,9,10,11], and for studying the binding of drugs[12]
The phospholipid layers were prepared on oxidized PDMS (ox-PDMS), PDMS, and glass through the fusion of small unilamellar vesicles (SUVs) composed of 99.9 mol % DOPC and 0.1mol % of the fluorescent phospholipid rhodamine-PE in Tris-HCl buffer containing 2 mM Ca2+
The phospholipid layer on PDMS appeared less bright than the layer on ox-PDMS and glass

Summary

Introduction

Nanometric phospholipid bilayers supported on a solid surface are cell membrane mimetic in vitro constructs useful for fabricating biosensors[1,2,3,4,5,6] for studying membrane biophysics[7,8,9,10,11], and for studying the binding of drugs[12]. Native PDMS is hydrophobic[23,24,25,26,27,28], plasma oxidation is required to make the surface of PDMS hydrophilic and suitable for supporting phospholipid bilayers. PDMS is used widely in soft-lithography, the temporal stability of phospholipid bilayers on plasma-oxidized PDMS (ox-PDMS) is not known. Such a study is useful, since the use of ox-PDMS as a biointerface, instead of glass, is advantageous in applications such as microfluidics[6], applications that require variations in topography and curvature [8,10,11,14,15,30], and applications that require dynamic changes in surface area[14,19]

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